linux-kernel - [PATCH] mm: only define hashdist variable when needed

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Message-Id: <1430753249-30850-1-git-send-email-linux@rasmusvillemoes.dk>
Date:	Mon,  4 May 2015 17:27:29 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Michal Hocko <mhocko@...e.cz>,
	David Rientjes <rientjes@...gle.com>
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH] mm: only define hashdist variable when needed

For !CONFIG_NUMA, hashdist will always be 0, since it's setter is
otherwise compiled out. So we can save 4 bytes of data and some .text
(although mostly in __init functions) by only defining it for
CONFIG_NUMA.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 include/linux/bootmem.h | 8 ++++----
 mm/page_alloc.c         | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index 0995c2de8162..f589222bfa87 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -357,12 +357,12 @@ extern void *alloc_large_system_hash(const char *tablename,
 /* Only NUMA needs hash distribution. 64bit NUMA architectures have
  * sufficient vmalloc space.
  */
-#if defined(CONFIG_NUMA) && defined(CONFIG_64BIT)
-#define HASHDIST_DEFAULT 1
+#ifdef CONFIG_NUMA
+#define HASHDIST_DEFAULT IS_ENABLED(CONFIG_64BIT)
+extern int hashdist;		/* Distribute hashes across NUMA nodes? */
 #else
-#define HASHDIST_DEFAULT 0
+#define hashdist (0)
 #endif
-extern int hashdist;		/* Distribute hashes across NUMA nodes? */
 
 
 #endif /* _LINUX_BOOTMEM_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ebffa0e4a9c0..159dbbc3375d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6013,9 +6013,9 @@ out:
 	return ret;
 }
 
+#ifdef CONFIG_NUMA
 int hashdist = HASHDIST_DEFAULT;
 
-#ifdef CONFIG_NUMA
 static int __init set_hashdist(char *str)
 {
 	if (!str)
-- 
2.1.3

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